Welding operation can be classified as manual welding, semi-automatic welding, and automated welding. Most welding is still performed without automation. Semi-automatic welding conventionally describes the automation of consumable feeding or the motorized feeding of consumable electrodes in gas metal arc welding (GMAW) and flux-cored arc welding (FCAW) processes. Nevertheless, the movement of the arc or electrode is still performed by a human weld operator and is therefore dependent on the skills of the human weld operator. American Welding Society estimates there will be a shortage of 290,000 welding professionals by 2020 and, in particular, a shortage of skilled welders. Such trends are not limited to the United States and do not bode well for the production of quality welds in the future to meet the growing fabrication demand.
Automated welding, either robotic or fixed/hard automation, has been a viable solution to remove human weld operator from the delicate task of holding the weld tool with proper orientation with respect to joint and travel direction, and moving the weld tool along the weld seam at proper speeds. Typically, a welding robot motion has two types, air moves and weld moves. The air moves are intended to move the weld tool from one weld position to another without actual welding. The weld moves are intended to perform a welding operation with the weld tool held by the robot. It is extremely effective in high-volume, low-mix repetitive autonomous welding tasks in a confined work cell completely isolated from people for safety. However, automation solutions have proven to be costly and intimidating to new users, and further require a robot technician to maintain and program. In addition, automation solutions are difficult to weld in confined spaces, joints, and weld large workpieces, such as buildings, bridges or ships. They are difficult to adapt to part fit-up variations, and often do not replace the weld operator, but rather only substitute the weld operator with a robot operator.
Due to the shortage of skilled welders, skilled welders are usually reserved for structurally critical welds at a shipyard or construction site. Weldments are normally tack welded together before a structural weld is put in. Tack welds are temporary short welds that hold the components of a weldment in place before the structural weld is applied. Since the tack weld might not have to pass the rigor of a weld inspection of the finished weld, temporary workers without weld qualification (e.g., shipyard labor such as painters, electricians, outfitters, plumbers, etc.) may be employed instead of skilled welders to perform tack welds. However, poor tack weld quality can contribute to weld defects in the final structural weld. Further, tack welding can be ergonomically taxing on the human operator. For example, thousands of small tack welds must be placed in ship panel stiffeners during a work day in which the human operator must bend over or kneel down to perform the tack weld. Such ergonomic issues can also affect tack weld quality as fatigue sets in.
Besides tack welds, many structures are made solely by short stitch welds (also known as a series of stringer beads or skip welds) that are sufficient to carry the load and maintain structural integrity. Designers use short segmented stitch welds in lieu of a continuous long seam weld to reduce total heat input to the weldment, thereby reducing distortion, heat affected zone, residual stress, and burn-through, and realizing weld consumable savings. Stitch welding is sometimes used to arrest the zipper effect in crack propagation. Moreover, structures such as bicycle frames are made with short tube-to-tube welds.
Those who perform occasional welding such as hobbyists, farmers, and repair shop workers need an easy way to make welds without the lengthy training typically required to become an expert in manipulating the welding torch.
Heat during the welding operation is a further consideration. As the automotive industry begins to use aluminum alloys and ultra high strength steel in car designs which might cause the emergence of an auto collision repair market for welding and brazing equipment and processes that are qualified by auto original equipment manufacturers (OEMs) for these materials. Machines that integrate the wire feeder and the welding power supply in one unit can be provided which offer ease of use, simplicity, and low cost, thereby making the machines useful for light fabrication activities, such as auto repair and light-duty manual welding in welding shops. Auto OEMs can specify the pulse welding process to be used with aluminum and the braze process for thin gauge advanced high strength material for use in production and in repair. The pulse weld process in such machines have proven to be too hot or use too much heat input for welding aluminum and brazing thin gauge advanced high strength steel. Arc length and width can be adjusted to balance low heat input with a wide arc for capillary effect to wet out the weld toes. In some instances, an optimum arc length and width cannot be determined to satisfy good wetting and no burn-through, for example. Conventional pulse on such machines also suffer from wire burn-back when welding out of position.
Panasonic offers robotic stitch welding or the ability to quickly turn on and off the arc and wire while moving the torch by a set distance before the next weld. This creates a string of overlapping spot welds and a stacked dime appearance. The benefit is an overall reduction in heat input because the arc is completely turned off between each spot weld, yet each spot has sufficient wetting. However the process is only offered on a robot, it is very tedious to do this manually. The robot is relied upon to stack the overlapping spot welds together to form an ultralow heat input weld. This is very expensive, and robotic welding is not feasible in many applications and environments.